In general, a photolithography process refers to a process where a photoresist film is evenly applied on a wafer, patterned by an exposure process using a photo mask formed in a predetermined lay-out, and then developed to form a pattern in a specific shape in the exposed photoresist film.
The photolithography technique used in the photolithography process in the fabrication of the semiconductor device utilizes an elaborate mask design so that it can properly control the amount of light transparently emitted from the mask. To this end, an optical proximity correction (OPC) technique and a phase shifting mask technique have been developed, and various methods capable of minimizing the phenomenon of light distortion due to a pattern shape drawn in the mask have been sought.
In particular, as design rule minimum sizes have decreased for a high-integration of a semiconductor device, a defect occurring in a pattern due to an Optical Proximity Effect with an adjacent pattern in the photolithography process has become a problem.
In other words, when forming a pattern in a quadrangular shape, a corner-rounding phenomenon where a corner of the quadrangular pattern becomes round due to light diffraction and interference occurs. Also, differences in pattern density can create problems due to the optical proximity effect where the patterns in an area where the patterns are isolated (such as an isolation area) are patterned to be small in size as compared to that in an area where the patterns are dense (dense area).
Such a technique to form a mask pattern affects the accuracy of the patterns formed on the semiconductor substrate. In particular, if the optical proximity effect of the mask pattern is not properly considered, the distortion of a pattern critical dimension occurs differently from the original exposure intention of the lithography, thereby many bad effects on the characteristics of the semiconductor device may occur.
In particular, when a regular rule is not applied between the pattern intervals formed in a dense area, it causes a problem where the amount of database DB required exceedingly increases when manufacturing a semiconductor device using a photo mask.